A validated HPLC‐MS/MS method for the quantification of caderofloxacin in human plasma and its application to a clinical pharmacokinetic study

A simple, selective and rapid HPLC‐MS/MS method was developed and validated for the determination of caderofloxacin in human plasma. Sparfloxacin was used as the internal standard (IS). After precipitation with methanol and dilution with the mobile phase, the samples were injected into the HPLC‐MS/MS system. The chromatographic separation was performed on a Zorbax XDB Eclipse C₁₈ column (150 × 4.6 mm, 5 µm) with a mobile phase of ammonium acetate buffer (20 mm, pH 3.0)–methanol, 45:55 (v/v). The MS/MS analysis was done in positive mode. The multiple reaction monitoring transitions monitored were m/z 412.3 → 297.1 for caderofloxacin and m/z 393.2 → 292.2 for the IS. The calibration curve was linear over the range of 50.0–8000 ng/mL with an aliquot of 100 μL plasma. The precision of the assay was 2.0–9.4 and 6.6–11.5% for the intra‐ and inter‐run variability, respectively. The intra‐ and inter‐run accuracy (relative error) was 4.4–10.0 and ?1.2–4.0%. The total run time was 3.5 min. The assay was fully validated in accordance with the US Food and Drug Administration guidance. It was successfully applied to a pharmacokinetic study of caderofloxacin in healthy Chinese volunteers. Copyright © 2015 John Wiley & Sons, Ltd.     

Development and validation of an LC‐ESI‐MS/MS method for the quantitation of hemslecin A in rhesus monkey plasma and its application in pharmacokinetics

In this study, a new LC‐ESI‐MS/MS‐based method was validated for the quantitation of hemslecin A in rhesus monkey plasma using otophylloside A as internal standard (IS). Hemslecin A and the IS were extracted from rhesus monkey plasma using liquid–liquid extraction as the sample clean‐up procedure, and were subjected to chromatography on a Phenomenex Luna CN column (150 × 2.0 mm, 3.0 µm) with the mobile phase consisting of methanol and 0.02 mol/mL ammonium acetate (55:45, v/v) at a flow rate of 0.2 mL/min. Detection was performed on an Agilent G6410B tandem mass spectrometer by positive ion electrospray ionization in multiple reaction monitoring mode, monitoring the transitions m/z 580.5 [M + NH₄]⁺ → 503.4 and m/z 518.2 [M + NH₄]⁺ → 345.0 for hemslecin A and IS, respectively. The assay was linear over the concentration range of 0.5–200 ng/mL and was successfully applied to a pharmacokinetic study in rhesus monkeys. Copyright © 2013 John Wiley & Sons, Ltd.     

A high performance liquid chromatography-tandem mass spectrometric method for the determination of mefenamic acid in human plasma: application to pharmacokinetic study

In the present study, the development and validation of an LC‐MS/MS method for quantifying mefenamic acid in human plasma is described. The method involves liquid–liquid extraction using diclofenac as an internal standard (IS). Chromatographic separation was achieved on a Thermo Hypurity C₁₈, 50 × 4.6 mm, 5 µm column with a mobile phase consisting of 2 m m ammonium acetate buffer and methanol (pH 4.5 adjusted with glacial acetic acid; 15:85, v/v) at a flow‐rate of 0.75 mL/min and the total run time was 1.75 min. Analyte was introduced to the LC‐MS/MS using an atmospheric pressure ionization source. Both the drug and IS were detected in negative‐ion mode using multiple reaction monitoring m/z 240.0 → 196.3 and m/z 294.0 → 250.2, respectively, with a dwell time of 200 ms for each of the transitions. The standard curve was linear from 20 to 6000 ng/mL. This assay allows quantification of mefenamic acid at a concentration as low as 20 ng/mL in human plasma. The observed mean recovery was 73% for the drug. The applicability of this method for pharmacokinetic studies has been established after successful application during a 12‐subject bioavailibity study. Copyright © 2012 John Wiley & Sons, Ltd.     

Simultaneous determination of vitexin and isovitexin in rat plasma after oral administration of Santalum album L. leaves extract by liquid chromatography tandem mass spectrometry

An LC‐MS/MS method was developed for the simultaneous determination of vitexin and isovitexin in rat plasma, using puerarin as the internal standard (IS). Plasma samples extracted with protein precipitation procedure were separated on a Diamonsil® C₁₈ column (150 × 4.6 mm, 5 µm) with a mobile phase composed of methanol and 0.1% formic acid (45:55, v/v). The detection was accomplished by multiple reaction monitoring mode in positive electrospray ionization source. The optimized mass transition ion‐pairs for quantitation were m/z 431.2 → 311.1 for vitexin and isovitexin, and m/z 415.1 → 295.1 for IS. The total run time was 7.5 min for each injection. The calibration curves were linear (r² > 0.99) over the investigated concentration range (2.00–2000 ng/mL) and the lower limits of quantification were 2.00 ng/mL in rat plasma sample. The intra‐ and inter‐day relative standard deviations were no more than 14.9% and the relative errors were within the range of ?3.2–2.1%. The extraction recoveries for both compounds were between 89.3 and 97.3%. The robust LC‐MS/MS method was further applied in the pharmacokinetic study in Sprague–Dawley rats after oral administration of Santalum album L. leaves extract at a dose of 116 mg/kg. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of a sensitive liquid chromatography/tandem mass spectrometry method for the determination of fenofibric acid in rat plasma

A rapid and sensitive LC‐MS/MS method for the quantification of fenofibric acid in rat plasma was developed and validated. Plasma samples were prepared by liquid–liquid extraction with a mixture of N‐hexane–dichloromethane–isopropanol (100:50:5, v/v/v). Isocratic chromatographic separation was performed on a reversed‐phase Discovery C₁₈ column (2.1 × 50 mm, 5 µm). The mobile phase was methanol–water–formic (75:25:0.25, v/v/v). Detection of fenofibric acid and the internal standard (IS) diclofenac acid was achieved by ESI MS/MS in the negative ion mode using m/z 317 → m/z 213 and m/z 294 → m/z 250 transitions, respectively. The method was linear from 0.005 to 1.250 µg/mL when 100 μL plasma was analyzed. The lower limit of quantification was 0.005 µg/mL. The intra‐ and inter‐day precision values were below 8.2%, and accuracy ranged from ?0.9 to 2.1% in all quality control samples. The recovery was 90.3–94.7% and 83.3% for fenofibric acid and IS, respectively. Total run time for each sample analysis was 2.5 min. The validated method was successfully applied to a pharmacokinetic study in six rats after oral administration of fenofibrate, the ester prodrug of fenofibric acid (equivalent to fenofibric acid 5 mg/kg). The method permits laboratory scientists with access to the appropriate instrumentation to perform rapid fenofibric acid determination. Copyright © 2011 John Wiley & Sons, Ltd.     

A validated LC–MS/MS method for the simultaneous determination of thalidomide and its two metabolites in human plasma: Application to a pharmacokinetic assay

An accurate and sensitive LC–MS/MS method for determining thalidomide, 5‐hydroxy thalidomide and 5′‐hydroxy thalidomide in human plasma was developed and validated using umbelliferone as an internal standard. The analytes were extracted from plasma (100 μL) by liquid–liquid extraction with ethyl acetate and then separated on a BETASIL C₁₈ column (4.6 × 150 mm, 5 μm) with mobile phase composed of methanol–water containing 0.1% formic acid (70:30, v/v) in isocratic mode at a flow rate of 0.5 mL/min. The detection was performed using an API triple quadrupole mass spectrometer in atmospheric pressure chemical ionization mode. The precursor‐to‐product ion transitions m/z 259.1 → 186.1 for thalidomide, m/z 273.2 → 161.3 for 5‐hydroxy thalidomide, m/z 273.2 → 146.1 for 5′‐hydroxy thalidomide and m/z 163.1 → 107.1 for umbelliferone (internal standard, IS) were used for quantification. The calibration curves were obtained in the concentrations of 10.0–2000.0 ng/mL for thalidomide, 0.2–50.0 ng/mL for 5‐hydroxy thalidomide and 1.0–200.0 ng/mL for 5′‐hydroxy thalidomide. The method was validated with respect to linear, within‐ and between‐batch precision and accuracy, extraction recovery, matrix effect and stability. Then it was successfully applied to estimate the concentration of thalidomide, 5‐hydroxy thalidomide and 5′‐hydroxy thalidomide in plasma samples collected from Crohn's disease patients after a single oral administration of thalidomide 100 mg.     

Development and validation of a rapid LC‐MS/MS method to quantify letrozole in human plasma and its application to therapeutic drug monitoring

A selective, rapid, and sensitive liquid chromatography–tandem mass spectrometry(LC‐MS/MS) method was developed and validated for the determination of letrozole (LTZ) in human plasma, using anastrozole as internal standard (IS). Sample preparation was performed by one‐step protein precipitation with methanol. The analyte and IS were chromatographed on a reversed‐phase YMC‐ODS‐C₁₈ column (2.0 × 100 mm i.d., 3 µm) with a flow rate of 0.3 mL/min. The mobile phase consisted of water containing 0.1% formic acid (v/v) and methanol containing 0.1% formic acid (v/v). The mass spectrometer was operated in selected reaction monitoring mode through electrospray ionization ion mode using the transitions of m/z 286.2 → 217.1 for LTZ and m/z 294.1 → 225.1 for IS, respectively. The method was validated for selectivity, linearity, lower limit of quantitation, precision, accuracy, matrix effects and stability in accordance with the US Food and Drug Administration guidelines. Linear calibration curves were 1.0–60.0 ng/mL. Intra‐ and inter‐batch precision (CV) for LTZ were <9.34%, and the accuracy ranged from 97.43 to 105.17%. This method was successfully used for the analysis of samples from patients treated with LTZ in the dose of 2.5 mg/day. It might be suitable for therapeutic drug monitoring of these patients and contribute to predict the risk of adverse reactions. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitative determination of rupestonic acid in rat plasma by high‐performance liquid chromatography–tandem mass spectrometry and its application in a pharmacokinetic study

A sensitive and specific high‐performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC‐ESI‐MS/MS) method was developed and validated for determination of rupestonic acid in rat plasma. Protein precipitation method was used to extract rupestonic acid and the internal standard (IS) warfarin sodium from rats plasma. The chromatographic separation was performed on an Agela Venusil XBP Phenyl column with an isocratic mobile phase consisting of methanol–0.1% formic acid in water (40:60, v/v), pumped at 0.4 mL/min. Rupestonic acid and the internal standard (IS) warfarin sodium were detected at m/z 247.2 → 203.1 and 307.1 → 161.3 in positive ion and multiple reaction monitoring mode respectively. The standard curves were linear over the concentration range of 2.5–5000 ng/mL (r² > 0.99). The within‐day and between‐day precision values for rupestonic acid at four concentrations were 4.7–5.7 and 4.4–8.7%, respectively. The method described herein was fully validated and successfully applied to the pharmacokinetic study after an intravenous administration of rupestonic acid in rats. Copyright © 2012 John Wiley & Sons, Ltd.     

Measurement of fexofenadine concentration in micro‐sample human plasma by a rapid and sensitive LC‐MS/MS employing protein precipitation: application to a clinical pharmacokinetic study

A simple, rapid and sensitive liquid chromatography/positive ion electro‐spray tandem mass spectrometry method (LC‐MS/MS) was developed and validated for the quantification of fexofenadine with 100 μL human plasma employing glipizide as internal standard (IS). Protein precipitation was used in the sample preparation procedure. Chromatographic separation was achieved on a reversed‐phase C₁₈ column (5 μm, 100 × 2.1 mm) with methanol : buffer (containing 10 mmol/L ammonium acetate and 0.1% formic acid; 70 : 30, v/v) as mobile phase. The total chromatographic runtime was approximately 3.0 min with retention time for fexofenadine and IS at approximately 1.9 and 2.1 min, respectively. Detection of fexofenadine and IS was achieved by LC‐MS/MS in positive ion mode using 502.1 → 466.2 and 446.0 → 321.1 transitions, respectively. The method was proved to be accurate and precise at linearity range of 1–600 ng/mL with a correlation coefficient (r) of ≥0.9976. The validated method was applied to a pharmacokinetic study in human volunteers following oral administration of 60 or 120 mg fexofenadine formulations, successfully. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of bencycloquidium bromide in dog plasma by liquid chromatography with electrospray ionization tandem mass spectrometry

A rapid, selective and sensitive liquid chromatography/tandem mass spectrometry (LC‐MS/MS) method was developed and validated for determining bencycloquidium bromide (BCQB) in beagle dog plasma. The plasma sample was deproteinized with methanol which contained l‐ethyl‐bencycloquidium bromide as internal standard, and supernantant was assayed by LC‐MS/MS. The chromatographic separation was performed on a Phenomenex C₁₈ column (100 × 2.0 mm, i.d., 3.0 μm) with a gradient programme mobile phase consisting of methanol and ammonium acetate (5 mm) containing 0.15% acetic acid and at a flow rate of 0.3 mL/min. Electrospray ionization in positive ion mode and selective reaction monitoring was used for the quantification of BCQB with a monitored transitions m/z 330.2 → 142.1 for BCQB and m/z 344.2 → 126.2 for IS. Validation results indicated that the lower limit of quantification was 0.05 ng/mL and the assay exhibited a linear range of 0.05–10.0 ng/mL and gave a correlation coefficient of 0.9998. The intra‐ and inter‐run precisions of the assay were 1.7–4.6 and 3.2–15.6%, respectively, and the intra‐ and inter‐day accuracies were ?8.8 to 1.1 and ?5.0 to 4.6%, respectively. The developed method was applied for the pharmacokinetic study of BCQB in beagle dogs following a single intranasal dose. Copyright © 2009 John Wiley & Sons, Ltd.     

Development and validation of an LC‐MS/MS method for the determination of mesalazine in beagle dog plasma and its application to a pharmacokinetic study

A simple, specific and sensitive LC‐MS/MS method was developed and validated for the determination of mesalazine in beagle dog plasma. The plasma samples were prepared by protein precipitation, then the separation of the analyte was achieved on a Waters Spherisorb C₆ column (150 × 4.6 mm, 5 µm) with a mobile phase consisting of 0.2% formic acid in water–methanol (20:80, v/v). The flow rate was set at 1.0 mL/min with a split ratio of 3:2. Mass spectrometric detection was achieved by a triple‐quadrupole mass spectrometer equipped with an electrospray source interface in positive ionization mode. Quantitation was performed using selected reaction monitoring of precursor–product ion transitions at m/z 154 → m/z 108 for mesalazine and m/z 285 → m/z 193 for diazepam (internal standard). The linear calibration curve of mesalazine was obtained over the concentration range 50–30,000 ng/mL. The matrix effect of mesalazine was within ±9.8%. The intra‐ and inter‐day precisions were <7.9% and the accuracy (relative error) was within ±3.5%. The validated method was successfully applied to investigate the pharmacokinetics of mesalazine in healthy beagle dogs after rectal administration of mesalazine suppository. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantitative determination of euphol in rat plasma by LC‐MS/MS and its application to a pharmacokinetic study

Euphol is a potential pharmacologically active ingredient isolated from Euphorbia kansui. A simple, rapid, and sensitive method to determine euphol in rat plasma was developed based on liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) for the first time. The analyte and internal standard (IS), oleanic acid, were extracted from plasma with methanol and chromatographied on a C₁₈ short column eluted with a mobile phase of methanol–water–formic acid (95:5:0.1, v/v/v). Detection was performed by positive ion atmospheric pressure chemical ionization in selective reaction monitoring mode. This method monitored the transitions m/z 409.0 → 109.2 and m/z 439.4 → 203.2 for euphol and IS, respectively. The assay was linear over the concentration range 27–9000 ng/mL, with a limit of quantitation of 27 ng/mL. The accuracy was between –7.04 and 4.11%, and the precision was <10.83%. This LC‐MS/MS method was successfully applied to investigate the pharmacokinetic study of euphol in rats after intravenous (6 mg/kg) and oral (48 mg/kg) administration. Results showed that the absolute bioavailability of euphol was approximately 46.01%. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of asperosaponin VI in dog plasma by high-performance liquid chromatography-tandem mass spectrometry and its application to a pilot pharmacokinetic study

A sensitive and rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method has been developed and validated for the determination of asperosaponin VI in beagle dog plasma using glycyrrhizic acid as the internal standard (IS). Plasma samples were simply pretreated with methanol for deproteinization. Chromatographic separation was performed on a Hedera ODS‐2 column using mobile phase of methanol–10 mm ammonium acetate buffer solution containing 0.05% acetic acid (71:29, v/v) at a flow rate of 0.38 mL/min. Asperosaponin VI and the IS were eluted at 2.8 and 1.9 min, respectively, ionized in negative ion mode, and then detected by multiple reaction monitoring. The detection used the transitions of the deprotonated molecules at m/z 927.5 → 603.4 for asperosaponin VI and m/z 821.4 → 645.4 for glycyrrhizic acid (IS). The assay was linear over the concentration range of 0.15–700 ng/mL and was successfully applied to a pilot pharmacokinetic study in beagle dogs. Copyright © 2011 John Wiley & Sons, Ltd.     

Development and validation of an enantioselective LC‐MS/MS method to quantify enantiomers of (±)‐TAK‐700 in rat plasma: lack of in vivo inversion of (+)‐TAK‐700 (Orteronel) to its antipode

A highly sensitive, specific and enantioselective assay has been developed and validated for the estimation of TAK‐700 enantiomers [(+)‐TAK‐700 and (?)‐TAK‐700] in rat plasma on LC‐MS/MS‐ESI in the positive‐ion mode. Liquid–liquid extraction was used to extract (±)‐TAK‐700 enantiomers and IS (phenacetin) from rat plasma. TAK‐700 enantiomers were separated using methanol and 5 mm ammonium acetate (80:20, v/v) at a flow rate of 0.7 mL/min on a Chiralcel OJ‐RH column. The total run time was 7.0 min and the elution of (+)‐TAK‐700, (?)‐TAK‐700 and IS occurred at 3.71, 4.45 and 4.33 min, respectively. The MS/MS ion transitions monitored were m/z 308.2 → 95.0 for TAK‐700 and m/z 180.2 → 110.1 for IS. The standard curves for TAK‐700 enantiomers were linear (r² > 0.998) in the concentration range 2.01–2015 ng/mL for each enantiomer. The inter‐ and intra‐day precisions were in the ranges 3.74–7.61 and 2.06–8.71% and 3.59–9.00 and 2.32–11.0% for (+)‐TAK‐700 and (?)‐TAK‐700, respectively. Both the enantiomers were found to be stable in a battery of stability studies. This novel method was applied to the study of stereoselective oral pharmacokinetics of (+)‐TAK‐700 and it was unequivocally demonstrated that (+)‐TAK‐700 does not undergo chiral inversion to its antipode in vivo. Copyright © 2012 John Wiley & Sons, Ltd.     

A UPLC–MS/MS method for comparative pharmacokinetics study of morusin and morin in normal and diabetic rats

The aim of this study was to establish and validate a rapid, selective and reliable ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) for simultaneous quantitations of morin and morusin, and to investigate their pharmacokinetics difference between normal and diabetic rats after oral administration. Plasma samples were pretreated via protein precipitation with acetonitrile. Genkwanin was used as internal standard (IS). Analytes and IS were separated on a Thermo Hypersil Gold C₁₈ column (50 × 4.6 mm, 3 μm) using gradient elution. The mobile phase consisted of acetonitrile and 0.1% formic acid in water at a flow rate of 0.5 mL/min. Mass spectrometry detection was carried out by means of negative electrospray ionization source and multipe‐reaction monitoring mode. The transitions of m/z 300.9 → 151.2 for morin, m/z 419.2 → 297.1 for morusin and m/z 283.1 → 268.2 for IS were chosen for quantification. Calibration curves were linear in the range of 1.01–504.2 ng/mL (r² ≥ 0.99) for morin and 1.02–522.3 ng/mL (r² ≥ 0.99) for morusin. The lower limit of quantification was 1.02 ng/mL for morin and 1.05 ng/mL for morusin. The extraction recovery was >85.1% for each analyte. No obvious matrix effect was observed under the present UPLC–MS/MS conditions during all of the bioanalysis. The stability study demonstrated that morin and morusin remained stable during the whole analytical procedure. The method was successfully applied to support the pharmacokinetic comparisons of morin and morusin between normal and diabetic rats.     

A simple,rapid and reliable liquid chromatography–mass spectrometry method for determination of methotrexate in human plasma and its application to therapeutic drug monitoring

A simple, rapid and reliable liquid chromatography–electrospray ionization tandem mass spectrometry method was established and validated for the determination of methotrexate in human plasma. After a straightforward protein precipitation by acetonitrile–water (70:30, v/v), methotrexate (MTX) and p‐aminoacetophenone (used as internal standard, IS) were separated on a Column C₁₈ column (50 × 2.1 mm, 3 µm; Column Technology, Fremont, CA, USA) using a gradient elution with mobile phase of acetonitrile and 0.03% acetic acid aqueous solution at a flow rate of 0.5 mL/min. The total chromatographic runtime was 5 min for each injection. Quantification detection was performed in a triple‐quadruple tandem mass spectrometer under positive mode monitoring the following mass transitions: m/z 455.3 → 308.3 for MTX and m/z 136.1 → 94.4 for IS. The calibration curve was linear over the range of 0.05–25.0 µmol/L with a lower limit of quantification of 0.05 µmol/L. The intra‐ and interday precisions were <5.2%, the accuracy varied from ?4.1 to 4.5%. The recovery was >94%. The LC‐MS/MS method showed an excellent agreement with the existing HPLC‐UV method using Passing–Bablok regression and Bland–Altman difference plot analysis. The validated LC‐MS/MS can be successfully applied to the routine therapeutic drug monitoring of MTX in clinical laboratories. Copyright © 2015 John Wiley & Sons, Ltd.     

LC‐MS/MS determination of pogostone in rat plasma and its application in pharmacokinetic studies

Pogostone is an important constituent of Pogostemon cablin (Blanco) Benth., and possesses various known bioactivities. A rapid, simple and sensitive liquid chromatography tandem mass spectrometry (LC‐MS/MS) method was developed for the analysis of pogostone in rat plasma using chrysophanol as internal standard (IS). The analytes were extracted with methanol and separated using a reversed‐phase YMC‐UltraHT Pro C₁₈ column. Elution was achieved with a mobile phase consisting of methanol–water (75:25, v/v) for 5 min at a flow rate of 400 μL/min. The precursor/product transitions (m/z) under MS/MS detection with negative electrospray ionization (ESI) were 223.0 → 139.0 and 253.1 → 224.9 for pogostone and IS, respectively. The calibration curve was linear over the concentration range 0.05–160 µg/mL (r = 0.9996). The intra‐ and inter‐day accuracy and precision were within ±10%. The validated method was successfully applied to the preclinical pharmacokinetic investigation of pogostone in rats after intravenous (5, 10 and 20 mg/kg) and oral administration (5, 10 and 20 mg/kg). Finally, the oral absolute bioavailability of pogostone in rats was calculated to be 70.39, 78.18 and 83.99% for 5, 10 and 20 mg/kg, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

A rapid and sensitive determination of aucubin in rat plasma by liquid chromatography-tandem mass spectrometry and its pharmacokinetic application

A sensitive, accurate, rapid and robust LC‐MS‐MS method for the quantification of aucubin, a major bioactive constituent of Aucuba japonica, Eucommia ulmoides and Plantago asiatica, was established and validated in rat plasma. Plasma samples were simply precipitated by adding methanol and the supernatant was chromatographed by a Diamonsil® C₁₈(2) column with the mobile phase comprising a mixture of 10 mm ammonium acetate in methanol and that in water with the ratio of 50:50 (v/v). Quantification of aucubin was performed by mass spectrometry in the multiple‐reaction monitoring mode with positive atmospheric ionization at m/z 364 → 149 for aucubin, and m/z 380 → 165 for catalpol (IS), respectively. The retention time was 2.47 and 2.44 min for aucubin and the IS, respectively. The calibration curve (10.0–30,000 ng/mL) was linear (r² > 0.99) and the lower limit of quantification was 10.0 ng/mL in the rat plasma sample. The method showed satisfactory results such as sensitivity, specificity, precision, accuracy, recovery, freeze–thaw and long‐term stability. This simple LC‐MS method was successfully applied in a pharmacokinetic study carried out in Sprague–Dawley rats after oral administration of aucubin at a single dose of 50 mg/kg. Herein the pharmacokinetic study of aucubin is reported for the first time. Copyright © 2011 John Wiley & Sons, Ltd.     

Development of an LC‐MS/MS method for quantification of kadsurenone in rat plasma and its application to a pharmacokinetic study

A sensitive and rapid LC‐MS/MS method was developed and validated for the determination of kadsurenone in rat plasma using lysionotin as the internal standard (IS). The analytes were extracted from rat plasma with acetonitrile and separated on a SB‐C₁₈ column (50 × 2.1 mm, i.d.; 1.8 µm) at 30 °C. Elution was achieved with a mobile phase consisting of methanol–water–formic acid (65:35:0.1, v/v/v) at a flow rate of 0.30 mL/min. Detection and quantification for analytes were performed by mass spectrometry in the multiple reaction monitoring mode with positive electrospray ionization m/z at 357.1 → 178.1 for kadsurenone, and m/z 345.1 → 315.1 for IS. Calibration curves were linear over a concentration range of 4.88–1464 ng/mL with a lower limit of quantification of 4.88 ng/mL. The intra‐ and inter‐day accuracies and precisions were <8.9%. The LC‐MS/MS assay was successfully applied for oral pharmacokinetic evaluation of kadsurenone using the rat as an animal model. Copyright © 2013 John Wiley & Sons, Ltd.     

Development and validation of a HPLC-MS/MS method for the determination of venlafaxine enantiomers and application to a pharmacokinetic study in healthy Chinese volunteers

An HPLC‐MS/MS method has been developed and validated for the determination of venlafaxine enantiomers in human plasma and applied to a pharmacokinetic study in healthy Chinese volunteers. The method was carried out on a vancomycin chiral column (5 µm, 250 × 4.6 mm) maintained at 25°C. The mobile phase was methanol–water containing 30 mmol/L ammonium acetate, pH 3.3 adjusted with aqueous ammonia (8:92, v/v) at the flow rate 1.0 mL/min. A tandem mass spectrometer with an electrospray interface was operated in the multiple reaction monitoring mode to detect the selected ions pair at m/z 278.0 → 120.8 for venlafaxine enantiomers and m/z 294.8 → 266.7 for estazolanm (internal standard). The method was linear in the concentration range of 0.28–423.0 ng/mL. The lower limit of quantification was 0.28 ng/mL. The intra‐and inter‐day relative standard deviations were less than 9.7%. The method was successfully applied for the evaluation of pharmacokinetic profiles of venlafaxine enantiomers in 18 healthy volnteers. Validation parameters such as the specificity, linearity, precision, accuracy and stability were evaluated, giving results within the acceptable range. Pharmacokinetic parameters of the venlafaxine enantiomers were measured in the 18 healthy Chinese volunteers who received a single regimen with venlafaxine hydrochloride capsules. The results show that AUC_(0–∞), C_max and t_1/2 between S‐venlafaxine and R‐venlafaxine are significantly different (p < 0.05). Copyright © 2010 John Wiley & Sons, Ltd.